Medical nebulizers for aerosolizing a liquid medicine that can be inhaled by a patient are well known devices commonly used for the treatment of certain conditions and diseases. Nebulizers have applications in treatments for conscious, spontaneously-breathing patients and for controlled ventilated patients.
In some nebulizers, a gas and a liquid are mixed together and directed against a baffle. As a result, the liquid is aerosolized, that is, the liquid is caused to form into small particles that are suspended in the air. This aerosol of the liquid can then be inhaled into a patient's respiratory tract. One way to mix the gas and liquid together in a nebulizer is to pass a quickly moving gas over a liquid orifice tip of a tube. The negative pressure created by the flow of pressurized gas is a factor that contributes to drawing the liquid out of the liquid orifice tip into the stream of gas and nebulize it.
Some of the considerations in the design and operation of nebulizers include regulation of dosages and maintenance of consistent aerosol particle size. In conventional nebulizer design, pressurized gas may entrain a liquid against a baffle on a continuous basis until the liquid in a reservoir is depleted. Continuous nebulization may result in a waste of aerosol during a patient's exhalation or during a delay between a patient's inhalation and exhalation. This effect may also complicate regulation of dosages because the amount of wasted aerosol may be difficult to quantify. Also, continuous nebulization may affect particle size and/or density. In addition, there may be excess medication lost to condensation on the nebulizer or mouthpiece during periods of non-inhalation. On the other hand, interrupted nebulization may also affect particle size and density as the nebulization is turned on and off.
There are several other considerations that relate to the effectiveness of nebulizer therapies. For example, it has been suggested that nebulization therapy is more effective when the generation of aerosol particles is relatively uniform, for example, producing particles of a particular size, particles within a range of sizes, and/or particles a substantial percentage of which are within a range of sizes. In addition, it may be advantageous for a nebulizer to be able to generate a large amount of aerosol quickly and uniformly so that a proper dosage can be administered.
A further consideration is the environment in which the nebulizer therapy may be administered. For example, a wall outlet at a hospital may supply pressurized gas for use with a nebulizer at a flow rate of 4 to 10 liters per minute in a range from 45 psi to 55 psi, whereas a home care compressor may supply pressurized gas for use with a nebulizer at a flow rate of 3-5 liters per minute and at pressures of 15 to 30 psi. Regardless of the environment in which the nebulizer therapy is administered, it is desirable to maintain and/or improve performance of nebulizers.
Additional considerations in the design and operation of nebulizers relate to the size and shape of the baffle, and the volume of liquid available for nebulization contained between the reservoir and the liquid orifice.
Accordingly, with these considerations taken into account, there is a need for an improved nebulizer.